1. Field of the Invention
The present invention relates to a lithographic printing plate printer in which an original film with an image recorded thereon is brought into close contact with a lithographic printing plate placed on a printing surface plate, and light from a light source is transmitted through the original film so as to print the image on the original film onto the lithographic printing plate. In addition, the present invention relates to a transport apparatus for a lithographic printing plate for discharging a printed lithographic printing plate the printing surface plate and for feeding an unprinted lithographic printing plate onto the printing surface plate.
2. Description of the Related Art
When an image is printed on a photosensitive material or a presensitized plate (hereafter referred to as a PS plate) for a lithographic process, an original film with the image recorded thereon is fed to a printer in a state in which the original film is attached to a transparent cover sheet. The original film needs to be attached accurately to the cover sheet, and this attaching operation is performed by making use of register marks recorded on the original film.
This cover sheet is provided with punch holes for positioning on a printing surface plate of the printer, and positioning pins project from the upper surface of the printing surface plate. A plurality of cover sheets are stocked and are automatically transported onto the printing surface plate of the printer, and positioning is effected as the positioning pins are inserted through the punch holes. In some cases, the attachment of the original film to the cover sheet is automatically carried out by an apparatus formed separately from the printer. Thus as an operator operates an operation start button, the transport of the PS plate onto the printing surface plate and the positioning of the PS plate, and the transport of the cover sheet and the positioning of the cover sheet can be carried out automatically.
However, with the above-described conventional apparatus, the original films need to be attached in advance to the cover sheets and stocked. The aforementioned apparatus for attaching the original-films to the cover sheets can be disposed adjacent to the printer, but a large space is required for the installation of this separate apparatus, and it is additionally necessary to take into consideration the alignment of transport passages for delivering and receiving the cover sheets between the two apparatuses.
In addition, since a system for transporting the cover sheets with original films attached thereto in the conventional printer is of a so-called batch type in which the original film is discharged from the position where it was inserted, there has been a drawback in that the cover sheets cannot be fed continuously.
Furthermore, in a case where the same image is printed onto a plurality of photosensitive materials on the printing surface plate, the conventional practice has been such that after a printed photosensitive material is discharged from the printing surface plate, an ensuing unprinted photosensitive material is fed onto the printing surface plate, and the original film is placed again thereon.
However, in such conventional control of the photosensitive materials, the sum of the period of discharging the photosensitive material from the printing surface plate and the period of feeding an ensuing photosensitive material onto the printing surface plate is totalized as the operating time. Hence, the operating efficiency has been poor.
For this reason, it is conceivable to adopt an arrangement in which the direction of feeding the photosensitive material onto the printing surface plate and the direction of feeding it out from the printing surface plate are set to be the same direction, and an ensuing unprinted photosensitive material is fed while the printed photosensitive material is being discharged. However, if the transporting direction thus becomes rectilinear, the apparatus becomes large in size, so that it is not desirable.
In particular, in the presensitized plate printer for printing an image of the original film onto the PS plate, since the PS plate has a large area, the direction of feeding the PS plate onto the printing surface plate and the direction of feeding it out from the printing surface plate are conventionally set to be mutually opposite. In other words, by causing the PS plates to undergo reciprocating motion, an attempt has been made to render the apparatus compact.